In the field of mobile communication network coverage, an electrical tilt antenna for a base station is one of many important devices for realizing network coverage. In addition, a phase shifter is the most important component of the base station electrical tilt antenna. The quality of the phase shifter has direct influence on performance of the electrical tilt antenna, and has further influence on coverage quality of the network. As a result, it is manifest that the phase shifter plays a key role in the field of mobile base station antenna.
For prior art phase shifters, there are two conventional means to realize phase shifting. One way is achieved by changing the electrical length of a signal path inside the phase shifter, and the other way is achieved by moving dielectric material inside the phase shifter, thus further changing transmission velocity of signal in the phase shifter, thereby continuous linear phase difference for the signal output from the phase shifter is being generated. As such, the phase shifting is realized.
However, a prior art phase shifter realizing phase shifting by loading a dielectric element has the following problems.
First, the dielectric element directly contacts the feeding network and as a result, during long-term movement, friction will exist between the dielectric element and feeding network, thereby influencing performance of circuit.
Second, when the dielectric element contacts the feeding network, especially when the element is directly disposed on the feeding network, force will be imposed on the network. This not only jeopardizes structural reliability of the phase shifter, but also introduces passive inter-modulation product.